1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method for forming a via hole or a contact hole in an interlayer insulating film with a low dielectric constant.
2. Description of the Prior Art
In recent years, because of the higher degree of integration and the higher density of the semiconductor integrated circuit device, an increase in the data transfer rate has become needed. Therefore, there is a trend in wiring material, changing from the conventional aluminum (Al) to copper (Cu) having low resistance. In addition, concerning the interlayer insulating film surrounding this wiring, a film with a low dielectric constant is now in demand, instead of the conventional SiO2 film (dielectric constant 4.0). Such a low dielectric constant film is, for example, a porous SiO2 film whose dielectric constant is less than 2.0.
However, since the porous SiO2 film formed by the film forming method of the prior art has a porous structure, it absorbs moisture when it is left in the air and when it is subjected to washing after the film formation. As a result, its dielectric constant is increased.
In particular, if a contact hole or a via hole is formed, sometimes the moisture is absorbed at the side wall of the opening.
Further, there is another problem in that the moisture penetrates to the interlayer insulating film to cause corrosion of the underlying wiring layer.
It is an object of the present invention to provide a semiconductor device manufacturing method capable of preventing increase in the dielectric constant of the interlayer insulating film by suppressing the moisture absorption of the interlayer insulating film even when the interlayer insulating film with the low dielectric constant is first formed and then the via hole or the contact hole is formed in the interlayer insulating film.
In the semiconductor device manufacturing method according to the present invention, the interlayer insulating film is a multilayered structure with a porous insulating film formed on an underlying nitrogen containing insulating film, or on any one of a SiOC containing insulating film, a SiOCH containing insulating film, and a SiOCHN containing insulating film, and with an opening formed in the interlayer insulating film.
The porous insulating film is quite suitable for use as the interlayer insulating film because it has a low dielectric constant, whereas corrosion of the wiring is likely to occur if the porous insulating film is directly formed on the wiring, because it has a high moisture penetration. However, in the present invention, an underlying nitrogen containing insulating film, or any one of a SiOC containing insulating film, a SiOCH containing insulating film, and a SiOCHN containing insulating film are provided under the porous insulating film. Therefore, since penetration of moisture is suppressed by the underlying insulating film, the corrosion of the wiring, etc., can be prevented.
In addition, after the step of forming the opening in the porous insulating film, a nitrogen containing insulating film is formed on the surface of the porous insulating film and on the inner surface of the opening by bringing the exposed surface into contact with a plasma of any one of an ammonia gas, a nitrogen gas, and an oxygen nitride gas.
Accordingly, since the overall surface of the interlayer insulating film is covered with the nitrogen containing insulating film, the penetration of moisture into the interlayer insulating film can be further suppressed.
Also, after the step of forming the opening in the porous insulating film, the opening is exposed to a CxHy gas plasma. Accordingly, since a cover insulating film in the form of a hydrocarbon layer containing CxHy, e.g., CH3, is formed on the surface of the side wall of opening in the porous insulating film, improvement in the moisture resistance can be further improved.